The annual cost of osteoporosis-related fractures in the US is $8 billion, most of which is borne by women in spite of an abundance of research on factors that might ameliorate the postmenopausal drop in bone mineral density (BMD). An important component of a lifelong prevention strategy would be to create methods for young women in the years 14-20 to maximize their bone mineral content and maintain it until menopause. This proposal will rigorously test two comprehensive lifestyle interventions, both oriented toward healthy diet and sustainable exercise, one based on individual counseling and the other on group intervention, against an attention control. The aim is to build bone and prevent bone loss among young women 14 to <16 years of age at recruitment. This trial draws upon our experience in 2 important studies of teens and nutrition--the Teen Lifestyle Project, DISC--and the ongoing fruit and vegetable study, DASH. The design is a parallel-group randomized clinical trial. with 300 participants equally divided among the groups, and measurements at baseline and three follow-ups to 27 months. This will provide power 0.90 to detect differences of l%-2% in TBBMD rates of change between groups. Secondary analysis will compare the achievement of the diet and exercise goals as compared to control, measured by objective markers (serum folate and carotenoids urinary sodium, lean body mass, accelerometer measure of physical activity) as well as by self-reports. The tertiary analysis will examine the same diet and exercise outcomes between the two intervention groups. and also in relation to process measures (adherence, evaluations, retention). The final analysis will explore potential causal pathways to bone mineral health involving a wider variety of factors, such as family history, biological and behavioral factors, hormonal influences and markers of bone metabolism. The investigators have a substantial amount of expertise in behavioral modification, research on teenage girls, nutrition and exercise interventions. They have substantial experience with assessment of bone mineral, body strength, exercise patterns, and diet, and with the biostatistical and qualitative research approaches required. The project will be carried out at the Kaiser Permanente Center for Health Research, a fully equipped research center with a mission of biomedical research in the public domain, in collaboration with the Oregon Health Sciences University.